This document reviews the literature on the definition and measurement of quality of home visiting programs designed to promote early childhood development, with a particular focus on those interventions aimed at enhancing child cognitive, language, and socio-emotional outcomes. After summarizing the evidence on home visiting programs in the United States and internationally, we discuss the key elements that define a high quality home visit. Next, we describe a range of instruments designed to measure both structural and process elements of quality of home visits, instances in which they have been used, and the results of their administration.